MCQ trap of the day
One question where the first answer that comes to mind is usually wrong. Answer it, then see exactly where students slip and how to think it through.
Trap library: 27 classic exam traps
Read the trap first, then check yourself on similar questions in the daily quiz.
[Time, Speed & Distance] A 150 m long train crosses a pole in 15 seconds. What is its speed in km/h?
Answer: 36
The trap: Most people stop at 150 ÷ 15 = 10 and tick the first option. That is metres per second.
Reasoning: 150 ÷ 15 = 10 m/s. Multiply by 18/5 to convert to km/h: 10 × 3.6 = 36 km/h.
[Percentage] A price is increased by 20% and then decreased by 20%. The net change is:
Answer: 4% decrease
The trap: The two 20% changes look like they cancel, but the second 20% is taken on a bigger number.
Reasoning: Final = 1.2 × 0.8 = 0.96 of the original, a 4% decrease.
[Profit & Loss] If the cost price of 10 articles equals the selling price of 8 articles, the profit percentage is:
Answer: 25%
The trap: The quick guess is (10 − 8) ÷ 10 = 20%, which divides by the wrong quantity.
Reasoning: Let CP of one = 1. Then 8 × SP = 10, so SP = 1.25 and profit = 25%.
[Average] What is the average of the first five prime numbers?
Answer: 5.6
The trap: Many students include 1, which is not prime.
Reasoning: The first five primes are 2, 3, 5, 7, 11. Sum = 28, average = 28 ÷ 5 = 5.6.
[Time & Work] A can finish a job in 10 days and B in 15 days. Working together, they finish it in:
Answer: 6 days
The trap: Averaging the two times (12.5) feels natural but rates add, not times.
Reasoning: Combined rate = 1/10 + 1/15 = 1/6 per day, so 6 days.
[Algebra] If a + b = 5 and ab = 6, then a² + b² equals:
Answer: 13
The trap: People square 5 and stop at 25.
Reasoning: a² + b² = (a + b)² − 2ab = 25 − 12 = 13.
[Interest] The difference between compound and simple interest on ₹1000 at 10% per annum for 2 years is:
Answer: ₹10
The trap: Many calculate the full interest instead of the difference.
Reasoning: SI = ₹200, CI = 1000 × (1.1² − 1) = ₹210. Difference = ₹10.
[Probability] Two fair coins are tossed. The probability of getting at least one head is:
Answer: 3/4
The trap: Thinking "head or tail, so half" ignores the four equally likely outcomes.
Reasoning: Outcomes: HH, HT, TH, TT. Only TT has no head, so P = 3/4.
[Polity] Which Article of the Constitution abolishes untouchability?
Answer: Article 17
The trap: Article 15 (prohibition of discrimination) is the commonly confused option.
Reasoning: Article 17 abolishes untouchability and makes its practice an offence.
[Polity] In India's parliamentary system, real executive power lies with:
Answer: The Council of Ministers headed by the Prime Minister
The trap: The President is the head of state, so many assume the President holds real power.
Reasoning: The President is the nominal head; the Council of Ministers (Article 74) actually exercises executive authority.
[Polity] Which of the following is NOT a Fundamental Right at present?
Answer: Right to Property
The trap: The Right to Property was a Fundamental Right earlier, so it looks familiar.
Reasoning: The 44th Amendment (1978) removed it from Part III; it is now a legal right under Article 300A.
[Science] Which is the hottest planet in the solar system?
Answer: Venus
The trap: Mercury is closest to the Sun, so it seems the obvious answer.
Reasoning: Venus has a thick CO₂ atmosphere and a runaway greenhouse effect, giving it the highest surface temperature.
[Science] The largest organ of the human body is the:
Answer: Skin
The trap: The liver is the largest internal organ and the largest gland, which causes confusion.
Reasoning: The skin is the largest organ overall. The liver is the largest internal organ.
[Science] Which gas is the most abundant in Earth's atmosphere?
Answer: Nitrogen
The trap: Oxygen is what we breathe, so it feels dominant.
Reasoning: Nitrogen makes up about 78% of dry air; oxygen is about 21%.
[Science] A light year is a unit of:
Answer: Distance
The trap: The word "year" suggests time.
Reasoning: A light year is the distance light travels in one year, roughly 9.46 × 10¹² km.
[Science] Which vitamin is synthesised in the skin on exposure to sunlight?
Answer: Vitamin D
The trap: Vitamin A and C are better-known and often guessed.
Reasoning: Sunlight (UVB) converts a cholesterol derivative in the skin into Vitamin D3.
[Geography] What is the capital of Australia?
Answer: Canberra
The trap: Sydney is the best-known city, so it is the common wrong tick.
Reasoning: Canberra was purpose-built as the capital as a compromise between Sydney and Melbourne.
[Geography] The world's largest desert by area, counting cold deserts, is:
Answer: Antarctic
The trap: People associate "desert" only with sand and heat.
Reasoning: A desert is defined by low precipitation. Antarctica (about 14 million sq km) is larger than the Sahara, the largest hot desert.
[English] Choose the correct sentence: "Neither of the boys ___ present."
Answer: is
The trap: "Boys" is plural, so people choose a plural verb.
Reasoning: "Neither" and "either" take a singular verb, so the answer is "is".
[English] He is one of the students who ___ topped the exam.
Answer: have
The trap: The word "one" pulls the verb to singular.
Reasoning: The relative pronoun "who" refers to "students" (plural), so the verb is "have".
[Reasoning] Pointing to a man, Riya says, "He is the son of my mother's only brother." The man is Riya's:
Answer: Cousin
The trap: Words like "mother" and "son" make people jump to brother.
Reasoning: Mother's brother is the maternal uncle, and his son is Riya's cousin.
[Reasoning] Find the next number: 2, 6, 12, 20, 30, ?
Answer: 42
The trap: The differences (4, 6, 8, 10) suggest +10 next, giving 40.
Reasoning: The differences increase by 2 each time, so the next difference is 12 and the term is 42 (n × (n + 1) with n = 6).
[Reasoning] A man walks 5 km north, 5 km east and then 5 km south. How far is he from the start?
Answer: 5 km
The trap: Equal legs feel like they should return him to the start.
Reasoning: North and south cancel, leaving only the 5 km east displacement.
[Economy] Which of the following is a direct tax?
Answer: Income tax
The trap: GST is the most talked-about tax, so it is the common guess.
Reasoning: A direct tax is paid by the person on whom it is levied. Income tax is direct; the others are indirect.
[Banking Awareness] When the RBI raises the repo rate, loan EMIs generally:
Answer: Rise
The trap: "Raising" feels like a benefit, so people think EMIs fall.
Reasoning: A higher repo rate makes bank borrowing costlier, so banks usually raise lending rates and EMIs on floating-rate loans increase.
[Banking Awareness] The reverse repo rate is the rate at which:
Answer: RBI borrows from banks
The trap: Repo and reverse repo are easy to swap.
Reasoning: In reverse repo the RBI borrows surplus funds from banks and pays them this rate, which absorbs liquidity.
[History] Who coined the slogan "Inquilab Zindabad"?
Answer: Hasrat Mohani
The trap: Bhagat Singh popularised it, so most people credit him.
Reasoning: Maulana Hasrat Mohani coined the slogan in 1921; Bhagat Singh and his comrades made it famous.